Scoop-trimmed hydraulic turbocouplings



Oct. 1, 1968 w. H. K. JAMES SCOOP-TRIMMED HYDRAULIC TURBOCOUPLINGS 5Sheets-Sheet l Filed Jan. 16, 1967 Oct. l, 1968 w. H. K. JAMES 3,403,514

SCOOPTRIMMED HYDRAULIC TURBOCOUPLINGS Filed Jan. 16, 1967 y 5Sheets-Sheet 2 Figi Oct. 1, 1968 w. H. K. JAMES SCOOP'TRIMMED HYDRAULICTURBOCOUPLINGS v 5 Sheets-Sheet 5 Filed Jan. 16, 1967 5V /ff/ PatentedOct. l, 1968 3,403,514 SCOOP-TRIMMED HYDRAULIC TURBOCOUPLINGS Walter H.K. James, London, England, assignor to Fluidrive Engineering Company,Limited, Isleworth, England Filed Jan. 16, 1967, Ser. No. 609,526 Claimspriority, application Great Britain, Jan. 18, 1966, 2,379/ 66 7 Claims.(Cl. 60-54) ABSTRACT F THE DISCLOSURE A scoop-trimmed hydraulicturbocoupling has a second, quick-emptying scoop which is forced intothe ring of liquid in the scoop chamber to effect abnormally rapidemptying of the coupling when a detector detects abnormal operationconditions, for example pulling-out of a synchronous electric motordriving the coupling or seizure of the driven load, requiringdisconnection of the coupling drive more quickly than can be effected bythe normal trimming scoop.

This invention relates to scoop trimmed hydraulic turbocouplings and topower transmission systems in which drive is transmitted throughscoop-trimmed hydraulic turbocouplings.

Scoop-trimmed hydraulic turbocouplings comprise vaned impeller andrunner elements which together define `a toroidal working circuit forthe working uid and a casing which rotates with the impeller and extendsaround the runner to form a scoop chamber into which extends a movabletrimming scoop. The scoop chamber is in communication with the workingcircuit and the scoop trims off the liquid from the scoop chamber andthereby from the working circuit. Liquid is conveyed from the scoop to areservoir, and is returned from the reservoir to the working circuit ata steady rate by a pump. In many cases a cooler for the liquid issuitably located in the flow path. The radial position of the scoop inthe scoop chamber determines the radial depth of liquid in the scoopchamber and thereby the quantity of liquid in the working circuit. Thisin turn determines the torque transmitted by the coupling. y

Thus the transmitted torque, and hence the transmitted power can beadjusted by adjusting the position of the scoop in the scoop chamber.

Scoop-trimmed hydraulic turbocouplings can thus be convenientlyincorporated in power transmission systems for use where the transmittedtorque is to be controllable. This enables the speed of a driven machineto be controlled and also enables the driving machine, for example anelectric motor, to be quickly run up to its operating speed beforeapplying the full load torque.

Adjustment of the scoop position, and hence the transmitted torque isoften effected automatically by a servomechanism in response to changesin operating conditions. In order to prevent hunting of theservo-mechanism due to over-shooting as ya result of too rapidadjustment of the scoop, the speed of movement of the scoop isdeliberately kept low. Thus the trimming scoop may take ten or eventwenty seconds to move through its full range of movement.

A scoop-trimmed turbocoupling according to the present inventionincludes a second movable scoop constructed as a quick-emptying scoopand actuating means for moving the quick-emptying scoop to empty thescoop chamber and thereby the working circuit in response to a signalfrom a detector for detecting an abnormal operating conditionnecessitating rapid reduction in the torque transmitted by the coupling.

The size of the outer diameter of the trimming scoop is restricted bythe other parts of the coupling. Accordingly, the wall thickness andthereby the mechanical strength of the tube can only be increased at theexpense of reducing the bore of the trimming scoop. This in turn wouldincrease the flow velocities in the trimming scoop, leading to thepossibility of turbulence and surging which may be reflected back intothe working circuit to upset the steady transmission of torque. It isthus in general not considered feasible to construct a satisfactorytrimming scoop which can also be used for rapid emptying of the couplingby being forced deeply into the rotating ring of liquid in the scoopchamber.

The quick-emptying scoop acts independently of the trimming scoop andcan therefore be designed for optimum performance in removing liquidfrom the scoop chamber and working circuit. Thus whereas the trimmingscoop may take 10 or 20 seconds to complete its travel, thequick-emptying scoop may complete of its travel from the working-circuitfull to the Working-circuit empty positions in four seconds so that inthis time interval the torque transmitted by the coupling may drop to nomore than a quarter of the full load value.

The quick-emptying scoop may remain stationary during normal operationof the coupling and of the trimming scoop with its scooping orifice justclear of the circuit full position.

Alternatively, the quick-emptying scoop and its actuating means may-move With the trimming scoop during normal operation, with the scoopingorifice of the quickempty-ing scoop retracted relative to the trimmingscoop so as to lie a short distance outside the radial level of liquiddetermined vby the scooping orifice of the trimming scoop. Thequick-emptying scoop then has less far to move if its operation becomesnecessary in the partially filled condition of the working circuit.

Both the trimming scoop and the quick-emptying scoop may be of differentdesigns best suited for the purposes they have to fulll. Thus thetrimming scoop tube mouth and section may be sized specifically to givegood regulation with minimum aeration of the liquid, whilst thequick-emptying scoop tube would be constructed specifically for veryrapid emptying.

Advantageously, -a diverter valve may be included in the supply conduitfrom the pump to the working circuit. The diverter valve is operatedsimultaneously with movement of the quick-emptying scoop and may forexample, be mechanically linked to it. When operated, the diverter valvediverts the pump output away from the working circuit, conveniently backinto the reservoir. The speed of operation of the quick-emptying scoopcan thereby be increased since the normally continuous supply of workingliquid to the working circuit is cut off.

Embodiments of the invention will now be described by way of examplewith reference to the accompanying drawings, in which:

FIG. l is a perspective view with parts cut away of a scoop-trimmedcoupling in accordance with the invention;

FIG. 2 is a side elevational view of the coupling shown in FIG. 1, theupper part of the figure being shown in vertical axial section;

FIG. 3 is a diagrammatic cross sectional view on the line III-III ofFIG. 2 showing a modified form of scoop operating gear in the normaloperating condition; and

FIG. 4 is a view corresponding to FIG. 3 showing the quick-emptyingscoop in its operational position for rapidly emptying the couplingunder emergency conditions.

The scoop-trimmed hydraulic turbocoupling shown in FIGS. l and 2 followsconventional practice in that it comprises a base 1, the interior ofwhich forms a sump for the working liquid and on which is mounted ahousing 2 supporting in a spherical bearing 3 co-axial input and outputshafts 4 and S, the input and output shafts being located relative toeach other by a bearing 6. Secured to the input shaft 4 is an impellercasing 7 carrying the impeller element 8 and a scoop chamber 9. A runnerelement 10 is secured to the output shaft 5. The impeller 8 is alsomounted on an impeller sleeve 11 which is rotatably supported by thespherical bearing 3. The impeller and runner elements 8 and 10 are vanedand together deine a toroidal working circuit W for the working liquidof the coupling. The working circuit W is in free communication with theinterior of the scoop chamber 9 through the gap between the impeller andrunner elements 8 and 10 at their radial outer peripheries.

Oil for filling the working circuit W is delivered by a motor drivenpump 12 from which the oil passes through a cooler 13 and a divertervalve 14 to an inlet pipe 15 which delivers oil to the working circuitthrough internal passages 16 within the housing 2.

A trimming scoop tube 17 is slidably mounted in the housing 2 andextends into the scoop chamber 9. The free end of the scoop tube 17 isformed with a scooping orifice 18 which dips into the annulus of oil inthe scoop chamber 9 and trims off oil into the scoop tube 17. At itsother end the scoop tube 17 is formed with an orice 19 through which theoil passes through an elbow 20 to a cylindrical de-aerator chamber 21which it enters tangentially to form a rotating oil film on the wallthereof. From the lower end of the chamber 21 the oil drops into thesump in the base 1.

The scoop tube 17 can be moved between its various operating positionsby a hydraulic or pneumatic actuator 22, the range of movement of whichis sufficient to move the scoop between one end position in which thescoop chamber 9 and working circuit W are empty and substantially notorque is transmitted and the other end position in which the workingcircuit W and scoop chamber 9 are full. Moreover the actuator 22 enablesthe scoop tube 17 to be heldin any desired intermediate positioncorresponding to the desired partial filling of the working circuit W.The actuator 22 is controlled by appropriate control gear which isconventional in the art and the precise nature of which is determined bythe installation in which the coupling is used. In general the speed ofmovement of the scoop tube 17 will be kept low in order to avoid huntingand overshooting of the control systems and thus of the transmittedtorque.

The coupling shown in FIGS. 1 and 2 differs from conventional practicein that it includes a second, quickemptying scoop tube 23 which isparallel to the` scoop tube 17 but mounted on the opposite side of thecoupling axis. The external diameter of the quick-emptying scoop tube 23may be the same as that of the scoop tube 17 but as clearly shown inFIG. 2 its wall thickness is greater, thereby imparting greaterrigidity. The quick-emptying scoop tube 23 terminates in a scoopingorifice 24 which is larger than the orifice 18. The scoop tube 23 isnormally located so that its scooping orifice 24 lies radially inwardsof the annulus of oil in the scoop chamber 9 so that under normaloperating conditions there is no flow through the quick-emptying scooptube 23 in any position of the control scoop tube 17. However, thequick-emptying scoop tube 23 can be forced further into the scoopchamber 9 under emergency conditions by an actuator 2S which is arrangedto operate much more rapidly than the actuator 22. The greater rigidityof the scoop tube 23 enables it to withstand the forces imposed on it bythis operation while its large scooping orifice 24 empties the workingcircuit W and scoop chamber 9 very rapidly.

The pressure supply to the actuator 25 is also applied to a conduit 26to actuate the diverter valve 14 to divert the ow from the cooler 13directly back into the sump through a conduit 27, thereby diverting theflow from the coupling inlet 15.

The relative orifice sizes and wall thicknesses of the control andquick-emptying scoop tubes 17 and 23 are shown by way of comparison inphantom outline in FIG. 2.

FIGS. 3 and 4 illustrate an alternative arrangement for operating thescoop tubes 17 and 23. In this arrangement the quick-emptying scoop tube23 moves with the control scoop tube 17 but is positioned so that itsorifice 24 is slightly nearer to the coupling axis than the controlscoop orifice 18 so that no liquid enters the orifice 24. Thus when anemergency occurs requiring the working circuit to be rapidly emptied,the scoop tube 23 only has to move a small distance for its orifice toenter the annulus of liquid in the chamber 9.

For this purpose the scoop tube 17 carries an arm 27' which in turncarries a lost motion device 28 which cooperates with a flange 29 on thequick-emptying scoop 23. The lost motion device 28 provides twoabutments 30 and 31. A spring 32 of sufficient stiffness to move thequickemptying scoop 23 under normal conditions is positioned between theabutment 31 and the flange 29.

The actuator 25' for the quick-emptying scoop is normally empty of fluidbut is provided with pressurised uid through the pipe 26' underemergency conditions.

Under normal conditions the actuator 22 moves the control scoop tube 17to the required positions. The arm 27', abutment 30 and spring 32 ensurethat the scoop tube 23 moves with the scoop tube 17. Under emergencyconditions however the quick-emptying scoop tube 23 is forced by theactuator 25 against the risistance of the spring 32 into its fullyoperating position in which it rapidly empties the working circuit W andscoop chamber 9 of the coupling.

When the invention is applied to scoop-trimmed couplings having twinworking circuits, that is having two impeller elements connectedtogether and two runner elements connected back to back and two scoopchambers, a quick-emptying scoop will be provided for each scoopchamber.

By way of example, two applications of the couplings described abovewill now be described in more detail.

The rst of these applications relates to synchronous electric motordrives.

It has recently been ascertained that within the approximate power rangeof 2,500 to 10,000 H.P. it may be preferable to employ a synchronouselectric motor with a variable filling fiuid coupling as being cheaper,more eicient and having better start-up characteristics than the moreusual squirrel-cage motor and coupling combination. The exact boundariesof this favourable horse-power zone depend to a certain extent on theactual application and the particular motor speed. Furthermore, theability to obtain power factor correction if desired with thesynchronous motor may confer substantial improvement in the operation ofthe complete plant.

However, synchronous motors are unfortunately very sensitive to supplyvoltage fluctuations or temporary supply interruptions. Thus, if thesupply voltage falls to zero within a quarter-of-a-cycle and thereafterthree seconds are required to restore full line voltage, then the motorwould drop out of synchronism and unless the load can be removed itwould not re-synchronise. Obviously, a variable filling fluid couplingis very suited to relieving the motor load during such voltage lossconditions. A further typical requirement is that within 15 seconds ofthe initial supply disturbance the motor must be back on line, the Huidcoupling full and normal drive restored. This requirement would arisefor example with a halfduty standby and start-up boiler feed pumprequired for a turbo-alternator boiler unit of, say, 500 mw. capacity.

Normally the fluid coupling scoop is controlled by a servo motorreceiving its signals from the automatic boiler control system in thecase of a boiler feed pump.

Therefore, the scoop tube would normally be moved at a rate determinedby this servo gear and to match the overall dynamics of the plant it maytake anything from l to 20 seconds for the scoop tube to be movedthrough its full travel from circuit full to circuit empty.

Therefore, if the normal scoops were to be used also to empty the uidcoupling very rapidly on loss of the synchronous motor supply voltage,then not only must the normal control gear be over-ridden, butfurthermore the scoops must be moved at a much faster rate. This wouldlead to complications with the control gear.

This diliiculty is overcome by the completely separate quick-emptyingscoop which is under the control of electrical equipment intendedspecifically to detect loss of motor supply voltage. A typical detectorwould be a power factor type pull-out relay of already well-knowndesign, see for example Out-of-Step Protection for Synchronous Motors byL. C. Trickey A.M.I.E.E. in AEI Engineering February 1961 (AssociatedElectrical Industries Limited, Manchester, England), and could be fittedwith automatic re-synchronising features.

The quick-emptying scoop is held normally at the circuit full positionuntil signalled to move, whereafter it would empty the uid coupling to asuicient degree within, say four seconds, that is to say the auxiliaryscoop tube would go through about 90% of the full travel in fourseconds, whereafter the iiuid coupling could not transmit more than,say, one-quarter full load torque. As soon as the main voltage isrestored, a suitable detector would again actuate the scoop 23 to movevery quickly to the circuit full position and the fluid coupling workingcircuit would be refilled by the oil pump to the level called for by thecontrol scoop tube 17 very quickly. Therefore, throughout the cycle thecontrol scoop tubeconnected to the usual automatic control equipmentneed not move, and on resumption of normal operation would continue toregulate the Huid coupling in the usual way.

The second application of the invention to be described in more detailrelates to the direct driving of main boiler feed pumps byturbo-alternator sets. In a typical example, a 275 mw. turbo-alternatorrunning at 3,000 r.p.m. drives an 8,000 H.P. boiler feed pump through ascoop trimming coupling having a double working circuit, that is havingtwo impellers, two runners and two scoop chambers with a trimming scoopin each chamber, the two runners being connected together back-to-back.

The uid coupling is particularly chosen to have a low minimum slip sothat the torque transmitted by the working circuit when the output isstalled is many times the nominal full load torque value.

In a normal motor-driven application, if the boiler feed pump shouldseize with the tiuid coupling circuits full, then the motor would beelectrically pulled out and the set would come to rest. In the case ofthe turbinedriven uid coupling, however, the horsepower rating of thefeed pump is very small compared with that of the turbine. Thus if thefeed pump were to seize, the `full stalled torque capacity of the iiuidcoupling would be generated in heat leading, of course, to an extremelyrapid rise in temperature of the oil acting as working liquid.

Here again, for reasons connected with the rest of the plant, thetrimming scoops are usually arranged to move at a rate not faster thanfull travel in, say, 10 to 20 seconds. Therefore, if a quick-emptyingscoop were provided for each circuit, they could have their servolactuating means responsive to the output of a temperature senser suchas a thermocouple in the oil leaving the working circuit. In the eventof the uid coupling stalling and a dangerous rise in temperatureensuing, the quick-emptying scoops would be moved very rapidly and thusempty the fluid coupling circuits and keep them empty.

I claim:

1. A scoop-trimmed hydraulic turbocoupling comprising vaned impeller andrunner elements which together dene a toroidal working circuit for theworking uid, a casing which rotates with the impeller and extends aroundthe runner to form a scoop chamber into which extends a movable trimmingscoop, the scoop chamber -being in communication with the workingcircuit, and wherein the coupling includes a second movable scoopconstructed as a quick-emptying scoop and actuating means `for movingthe quick-emptying scoop to empty the scoop chamber and thereby theworking circuit in response to a signal from a detector for detecting anabnormal operating condition necessitating abnormally rapid reduction inthe torque transmitted by the coupling.

2. A coupling according to claim 1, wherein the quickemptying scoop isarranged to remain stationary during normal operation of the couplingand of the trimming scoop with its scooping orifice just clear of thecircuit full position.

3. A coupling according to claim 1, wherein the quickemptying scoop andits actuating means may move with the trimming scoop during normaloperation, with the scooping orice of the quick-emptying scoop retractedrelative to the trimming scoop so as to lie a short distance outside theradial level of liquid determined by the scooping orifice of thetrimming scoop.

4. A coupling according to claim 1, wherein liquid is delivered to theworking circuit by a pump and the coupling includes a diverter valve fordiverting the said liquid from entering the working circuit on actuationof the quick-emptying scoop.

5. A coupling according to claim 1, wherein the quickemptying scoop hasthicker walls and a larger scooping oriice than the main trimming scoop.

6. A coupling according to claim 1, wherein the said detector is a powerfactor pull-out relay associated with a synchronous electric motorconnected to drive the coupling.

7. A coupling according to claim 1, wherein the said detector is athermally sensitive device responsive to temperature increases in theliquid leaving the working circuit.

References Cited UNITED STATES PATENTS 2,264,341 12/1941 Sinclair et al60-54 2,428,005 9/1947 Bennett 60-54 XR 2,492,456 12/ 1949 Becker 60-54XR 3,320,748 5/ 1967 Nelden 60-54 FOREIGN PATENTS 762,371 11/1956 GreatBritain.

EDGAR W. GEOGHEGAN, Primary Examiner.

